| Near surface geophysics is ready to play an important role in the geotechnical engineering, because only geophysical techniques can provide the spatial information of the near surfaces in 2D, 3D, and 4D. Conventional geotechnical boring, one of the major investigation methods of the near surfaces, provides sparse and discrete information in 1D space, and used to estimate 2D sections assuming a horizontally layered structure on the premise that the surface layers are to be laterally homogeneous in a certain range. The supposition may be valid for the natural sediments, but is mostly inapt for manmade or artificial formations, because they are characterized as substantially inhomogeneous and irregular. Regretfully, near surface geophysicists have not had enough knowledge on the inhomogeneity of the near surface, especially of manmade formations. Recent studies on highresolution and integrated geophysical investigations have revealed that small scale irregularity is common in the near surfaces not only in manmade formations but also natural sediments especially fluvial sediments. Conversely, the near surface geophysics should image such irregular structures for the assessment of infrastructures and the bearing layer. Integration of several geophysical techniques is essential for deep understanding of the shallow layers. Moreover, near surface geophysicists should stand in the viewpoint of target oriented instead of method oriented. To establish the standing position, we have to be utility players of high-resolution geophysics and to choose appropriate methods according to the stage from planning to the maintenance of infrastructures. |
